Spirometra mansonoides is a species of tapeworm which secretes a proteinaceous factor capable of stimulating growth in some vertebrate species. Growth has been observed in mice, rats and hamster infested with the third larval stage of this worm, the plerocercoid or sparganum. In addition the growth factor is secreted when spargana are kept under in vitro culture conditions. It is the purpose of this project to maintain the S. mansonoides plerocercoids in culture for brief periods and to harvest the growth factor from the media. Once a sufficient quantity of material has been accumulated, the sparganum growth factor (SGF) will be purified and characterized. In particular, the properties of SGF will be compared with those of a variety of well characterized vetebrate growth hormones (GH), since SGF has been shown to produce many of the biological effects of mammalian growth hormones. This comparison can yield valuable insights into the chemical relationship of SGF and GH, as well as the mechanism of action of GH and perhaps the structural features of GH necessary for its biological activity. In addition, purified SGF is essential for studies on the role of SGF in the tapeworm itself or its natural host species, about which nothing is known.